APPLICATION OF THE QUASI-LONG CHAIN APPROXIMATION TO STRUCTURAL PERTURBATIONS IN POLYMETHINE DYES

A topological approach is presented for the treatment of the optical and chemical behaviour of polymethine dyes, and which can be regarded as a theory for structural perturbations of a polymethine chain caused by arbitrary end-groups. The theoretical basis of the method is discussed in terms of Green's functions, and various alternative ways to the formalism developed are reviewed briefly. Special attention is paid to a simple computational technique or estimating certain molecular parameters. A variety of applications of the method are considered, namely in the research for stable infrared polymethine dyes, the design of structural modifications to yield desired spectral effects, and the determination of the electrophilic and nucleophilic reaction centres in heterocycles.